parallel (version 3.3)

makeCluster: Create a Parallel Socket Cluster

Description

Creates a set of copies of Rrunning in parallel and communicating over sockets.

Usage

makeCluster(spec, type, ...)
makePSOCKcluster(names, ...)
makeForkCluster(nnodes = getOption("mc.cores", 2L), ...)
stopCluster(cl = NULL)
setDefaultCluster(cl = NULL)

Arguments

spec

A specification appropriate to the type of cluster.

names

Either a character vector of host names on which to run the worker copies of R, or a positive integer (in which case that number of copies is run on localhost).

nnodes

The number of nodes to be forked.

type

One of the supported types: see Details.

...

Options to be passed to the function spawning the workers. See Details.

cl

an object of class "cluster".

Value

• An object of class c("SOCKcluster", "cluster").

Details

makeCluster creates a cluster of one of the supported types. The default type, "PSOCK", calls makePSOCKcluster. Type "FORK" calls makeForkCluster. Other types are passed to package snow.

makePSOCKcluster is an enhanced version of makeSOCKcluster in package snow. It runs Rscript on the specified host(s) to set up a worker process which listens on a socket for expressions to evaluate, and returns the results (as serialized objects).

makeForkCluster is merely a stub on Windows. On Unix-alike platforms it creates the worker process by forking.

The workers are most often running on the same host as the master, when no options need be set.

Several options are supported (mainly for makePSOCKcluster): [object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Function makeForkCluster creates a socket cluster by forking (and hence is not available on Windows). It supports options port, timeout and outfile, and always uses useXDR = FALSE.

It is good practice to shut down the workers by calling stopCluster: however the workers will terminate themselves once the socket on which they are listening for commands becomes unavailable, which it should if the master Rsession is completed (or its process dies).

Function setDefaultCluster registers a cluster as the default one for the current session. Using setDefaultCluster(NULL) removes the registered cluster, as does stopping that cluster.